This invention relates to cutters of the kind having reciprocating knives and commonly used for cutting sheet material such as layups of fabric used for garments or upholstry, and deals more particularly with the drive mechanism of such a cutter for converting the rotary motion of a drive member into the reciprocating motion of the knife.
Reciprocating knife cutters conventionally drive the knife by means of a simple drive linkage consisting of a connecting link or rod connected between a driving eccentric pin or the like and the associated end of the knife. Such a drive mechanism, however, during various portions of each cycle of reciprocation imposes relatively large lateral forces on the connection between the connecting rod and the knife and, therefore, requires a relatively sturdy structure to resist such forces and generates a high degree of wear between the relatively moving parts. These lateral forces and the fact that the connecting rod has a substantial range of angular movement relative to the knife during each reciprocation cycle also complicates matters in cases where it is desired to rotate the knife about its axis of reciprocation relative to the connecting rod.
Further, knife driving mechanisms conventionally used in the past have tended to be relatively massive, bulky and subject to vibration problems.
The general object of this invention is, therefore, to provide a knife driving mechanism for a sheet material cutter which mechanism may be made of a relatively small size and light weight construction, which is relatively smooth in operation, which minimizes wear between the surfaces which guide the knife in its reciprocating movement, and which is suited to relatively high speed operation.
In particular, another object of this invention is to provide a drive mechanism of the foregoing character wherein the drive forces imposed on the knife occur substantially along its axis of reciprocation and whereby such result is achieved by means of only a small number of parts of simple construction and arrangement.
A still further object of this invention is to provide a drive mechanism for a reciprocating knife which lends itself to combination with other parts for rotating the knife about its axis of reciprocation and/or for raising and lowering the knife to bring it into and out of cutting relationship with the material being cut or to adjust the depth of knife penetration, as may be desired in the case where the cutter is part of an automatically controlled cutting system, such as shown in U.S. Pat. No. 3,548,697, wherein it is mounted on a carriage located above the surface of the material being cut and automatically moved relative thereto in a plane parallel to such surface.
Other objects and advantages of the invention will be apparent from the drawing and from the following detailed description of the preferred embodiment.